This invention relates to a detonator system and to a detonator and a connector for use in a detonator system.
An electronic detonator system can be constructed in different ways. In one approach use is made of a plurality of identifiable detonators which are connected to a two-wire bus. The unique identity of each detonator allows the individual detonators to be correctly addressed.
In another approach use is made of a so-called “daisy chain” in which the wiring order of the detonators is established by control equipment connected to a multi-wire bus. The wiring order is important for it allows each detonator to be distinguished from the others.
In certain blasting situations, particularly where regular timing delays are programmed into each detonator, the connection order of detonators can be used to establish a blast timing pattern, and a daisy chain system may be preferable in this application. A drawback is that, generally, three or four wires are required to make suitable connections to the detonators. The cost per detonator in this type of system is often higher than in a similar two-wire system. Reliability is also adversely impacted as the use of more wires requires correspondingly more connections and this increases the prospect of connectivity problems.
PCT/AU2006/000315 describes an electronic blasting system in which detonators are connected to a surface harness by two-wire leads. A respective actuator is positioned between each adjacent pair of detonators. The actuator is responsive to a command signal from a control unit. This means that the actuator must possess the capability to identify, and then respond to, the command signal which may be one of a plurality of possible signals. The inherent requirement for intelligence on-board the actuator increases the complexity of the actuator and thus increases the cost of a detonator system based on the use of a plurality of the actuators.
U.S. Pat. No. 4,846,066 discloses detonators which are connected so that programming signals will only be received by a given detonator when an adjacent detonator, nearer to a signal output, has been programmed. This is achieved by making use of a respective connector which is associated with each detonator and which includes a switching device which is operated by a logic element. Signals can only pass beyond a connector when a detonator which is associated with that connector has been programmed. To do this an additional wire is presumed to be required between the detonator and the connector. This feature increases the cost, and decreases the reliability, of a detonator system which makes use of this technique. The patent specification is silent regarding the use of the detonator wires for the transmission of logic signals.
ZA2009/06238 describes a system in which two-wire detonators are connected successively to a two-wire bus with appropriate connectors. Each connector includes a timer which initiates a timing interval and a switch, responsive to an end of the timing interval, to effect an electrical connection between control equipment and a detonator associated with the connector. This approach, which allows the detonators to be enumerated (identified), is relatively slow since the duration of the time interval, typically nominally the same for each connector, must permit for possible multiple communication attempts on the bus, before a following detonator is connected, to ensure that the system can function in noisy signal environments. Also, the control equipment is unable to effect a change in state of a connector even if communication with an associated detonator is successful on a first attempt.
An object of the present invention is to provide a detonator system wherein detonators and connectors can be connected to a two-wire bus without the passing of a time interval of fixed duration between successive connections.
Another object is to provide a low-cost connector of relatively simple construction for use in a detonator system.